INTRODUCTION. 3 



the early colonial days. These fall into three classes, political, 

 geometrical and natural, with reference to the areas of which 

 they treat. To political areas 590 titles are referred, upon 

 examination of the whole list; to geometrical, 142 titles and to 

 natural areas only 59 titles. The more popular methods do 

 not, however, afford so good a field for scientific grouping of 

 facts nor do they permit, without a most tedious and pains- 

 taking tabulation and criticism, any particularly useful gener- 

 alisations which might be based upon the facts when properly 

 arranged. For there is, apparently no very close connection 

 between those conditions which govern the boundary-lines of a 

 political district and the distribution of plants within those 

 boundaries. The boundaries of Minnesota are certainly not 

 'accidental, but have been fixed through the interaction of a 

 complicated series of causes and events, many of them too 

 subtile and elusive to permit of classification. Just as certainly 

 the kinds of plants in Minnesota, their relative abundance or 

 scarcity, their positions in forest, lake or meadow, their general 

 or local distribution are determined by a similarly complicated 

 and interlocking series of causes and events, many of which will 

 also, it is probable, be found to be too difficult and hidden for 

 successful analysis. In the effort to unravel somewhat of the 

 problems suggested, it is necessary that attention should not 

 be diverted to something quite extraneous or superficial and, 

 therefore, just as we should not attempt to interpret the laws 

 governing the action of a constitutional convention, by periodic 

 examinations of a mercury-barometer, no more should we 

 attempt to investigate the laws of plant-distribution in Minne- 

 sota by adhering to the artificial lines which separate it from 

 adjacent commonwealths or divide it into counties, towns or 

 sections. 



The Minnesota valley as a natural area. When one endeav 

 ors to divide the state of Minnesota into natural regions for the 

 purpose of prosecuting a botanical survey, the river-valleys at 

 once present themselves as suitable areas. As is well-known 

 Minnesota lies squarely at the crest of the North American 

 continent. Its altitude above the sea is less than that of other 

 places which might be named; but notwithstanding this it is 

 within its borders that the three great river systems of the 

 continent find their head-waters. Flowing northward is the 

 Red river, the principal tributary to Hudson Bay ; flowing 

 eastward is the St. Lawrence, the principal tributary to the 

 Atlantic, and flowing southward is the Mississippi, the great 



